1. Field of the Invention
The present invention relates to a sewing machine and, in particular, to a multi-needle sewing machine such as a multi-needle color-changing embroidery machine or stitchwork sewing machine comprising a machine head having a plurality of needle bars.
2. Description of the Related Art
The sewing machines now widely used include a single-needle sewing machine having a single needle and a multi-needle sewing machine having a plurality of needles. The multi-needle sewing machine is operated by driving a plurality of the needles alternately to form stitching or an embroidery in a plurality of colors on the sewing material.
FIG. 8 is a perspective view of a conventional multi-needle sewing machine. As shown in FIG. 8, a substantially cylindrical arm 300 is arranged on a table 200 of a multi-needle sewing machine 100 according to the prior art. A plurality of needle bars 410 are movably mounted vertically in a support case 400 provided at the forward end of an arm 300. A sewing needle 420 is arranged at the forward end of each of the needle bars 410, and a plurality of types of threads extending from a plurality of thread supply units (not shown) are connected to the needles 420 through a stitch balancing thread tensioner 430 and a balance 440. The support case 400 can be moved in X direction perpendicular to the axial line of the arm 300 by a needle bar select motor 450. As a result, the driving force from a motor (not shown) in the arm 300 can be selectively transmitted to a specific needle bar 410.
As shown in FIG. 8, two rails 210, 220 extend in parallel to each other from an end portion of the table 200. A bed 250 extending in a substantially horizontal direction from an end portion of the table 200 toward a lower place of the support case 400 is arranged between the rails 210, 220. Further, a horizontal drive mechanism 500 is arranged on the table 200. The horizontal drive mechanism 500 includes a Y-direction movement frame 510 movable in Y direction parallel to the axis of the arm 300 along the rails 210, 220 and a X-direction movement frame 520 movable in X direction perpendicular to the axis of the arm 300 along a base 590 forming the Y-direction movement frame 510. The X-direction movement frame 520 of the horizontal drive mechanism 500 shown in FIG. 8 carries a embroidery frame unit 800, and therefore the embroidery frame unit 800 can be moved to the desired position by motors (not shown) connected to each of the Y-direction movement frame 510 and the X-direction movement frame 520.
The embroidery frame unit 800 of the conventional multi-needle sewing machine 100 described above, however, is arranged inside the rails 210, 220 extending from the table 200. Therefore, the range of X-direction movement of the embroidery frame unit 800, i.e. the embroidery range is limited to between the rails 210 and 220. By increasing the distance between the rails 210 and 220, the range of X-direction movement of the embroidery frame unit 800 can also be increased. In such a case, however, the multi-needle sewing machine becomes bulky as a whole. In similar fashion, in the case wherein the length of the rails 210, 220 is increased to increase the range of Y-direction movement, the size of the multi-needle sewing machine 100 is increased. In such cases, the installation space of the multi-needle sewing machine 100 is increased while at the same time making it difficult to transport and deliver the multi-needle sewing machine 100.
Also, the arm 300 of the conventional multi-needle sewing machine 100 is often formed as a cylinder having a comparatively large thickness of 5 mm, so that the weight of the multi-needle sewing machine 100 is considerably increased. A resin cover such as a plastic cover may be arranged around the arm 300 to achieve the desired shape of the multi-needle sewing machine 100. As the arm 300 has a cylindrical structure, however, a wasteful space may be formed between the arm 300 and the resin cover, often resulting in a bulky body, of the multi-needle sewing machine 100, as a whole.
The present invention has been developed in view of the situation described above, and the object thereof is to provide a comparatively compact and lightweight multi-needle sewing machine capable of embroidery without being limited by the distance between the rails parallel to the arm.